I have an Enya 90-4C that I recently cleaned and reassembled. The problem I'm facing now is that the prop is compressing better in the wrong direction. I'm getting compression turning the prop clockwise (when facing the front of the plane), and hardly any when I spin it counterclockwise. Could I have connected the prop/crank to the piston arm incorrectly? Perharps I connected the crank when the piston arm was facing / this way instead of \ facing that way? I don't think it would make that big of a deal, the piston should still compress. Both valves are find, rockers are working...Any hints?

It depends on which side of the piston that the ring gap is on as to which direction you have compression.

Four strokes are not critical about which way the piston is

But it is best not to disturb the ring postion in the cylinder

The rod goes in a certain way - there is a front side and back side

Always put things back like you found them.

Did you remove the crankshaft or the cam from the crankcase? If so, you may not have the gears aligned correctly. There should be a pair of marks (one on the cam and one on the crankshaft) that need to be matched up. If they aren't, the valves will be opening and closing at the wrong times. I would double check this first.

Chuck

I did remove the cam gears. I aligned per my picture and per the instructions. Enya's have a small dot on each gear and two groves on the crank. Aligned how they should be, valves opening in the right sequence, just compression in the wrong directions. So either it is a clockwise turning engine (doubtful), or it has to due with the crank and the piston arm. I'll take it back out tonight and see if flipping the direction of the piston arm to works.

Make certain that you do not turn the connecting rod around backwards

The side that goes towards the front has a small chamfer or taper on the very edge that goes towards the crankshaft counter weight.

The back side will have little funny swirl marks on the face that go every which way.

It is troublesome on an Enya four stroke about the cam gears. If you swap them from side to side you will reverse the rotation of the engine even though the marks are aligned. Read your instructions carefully

If the carb is on and the throttle closed, it will show more comp. turning backwards, as it gets a snootfull of air with the open ex.. With the throttle closed, it can't get much air so it has lower comp. Really sucks ay.